1. Field of the Invention
The invention relates to a frame which connects electronic plug-in units to an integrating rack.
2. Description of the Prior Art
Electronic plug-in units are used in the Global System for Mobile Communications (GSM) to transmit and/or receive information via radio antennas to which these plug-in units are connected.
In some cases the radio beams thus formed are disturbed by the environment, in particular by foul weather such as rain or snow, for example. These disturbances adversely affect the quality of the radio link.
To remedy this problem, the electronic functions provided by the plug-in units are duplicated, optionally with a frequency change and/or connection of another plug-in unit to another antenna. Moreover, two duplicated plug-in units act as a mutual safeguard.
A security-protected cabinet is often used. This security-protected cabinet is in the form of a frame in which two transmitting/receiving units, also called PRUs (PRocessing Units), and a switching unit are fixed. Furthermore, a motherboard placed on the rear panel of the frame makes it possible to interconnect these three units.
The transmitting/receiving units or PRUs have a multiplexer electronic card, a power converter card and a modem card. Depending on the case, these two PRUs are connected to one and the same external antenna or to two separate external antennas which transmit and/or receive at a different frequency.
As regards the switching unit, this has an electronic switching card and a network management card. When each transmitting/receiving unit or PRU is connected to a separate external antenna, the switching unit firstly analyses the quality of the radio link of each unit and then it switches to the unit which has the better quality. In this case, the function of the switching unit therefore consists in providing a backup for the radio link.
On the other hand, if both transmitting/receiving units or PRUs are connected to one and the same antenna, the switching unit continually analyses the electronic state of these two units and when it detects a fault in a first unit, it switches to the second unit provided as a back-up. In this case, the switching unit makes it possible to manage the replacement of a defective transmitting/receiving unit with a back-up unit.
The invention will be described in this context without, however, being limited to radio-transmission applications or applications of backing up one PRU with another.
The depth of the electronic plug-in units is generally about 240 mm. Moreover, the frame, in which the plug-in units are fixed, is often fitted into and fixed in a standard integrating rack, i.e. in a cabinet, for example, the depth of which is standardized and equal to 450 mm or to 600 mm.
Only the switching unit has, on its front panel, external connection pins allowing it to be connected to other electronic modules.
However, these connection pins often protrude, from the front of the cabinet, so that it becomes impossible to close the door of the cabinet. What is more, because of this protrusion, it often happens that people, passing a little too close to the cabinet, brush against the connection pins, which results in a deterioration of their quality.
To avoid having the connection pins protruding from the front of the cabinet, it would seem to be necessary to move the plug-in units back towards the back of this cabinet. However, the current cabinets do not allow the plug-in units to be moved in the integrating rack. This is because a conventional frame is attached to the integrating rack so that it is impossible to move it towards the rear of the integrating rack. The plug-in units may be attached to the rack and can only be connected to the frame. In addition, the depth of the frame is fixed so that the plug-in units cannot be moved towards the rear of the frame, thereby simplifying their mode of connection. Consequently, from one installation to another, in a field, two types of frames, of different depths, must be available for allowing all requirements to be met.